Question

If the thickness of a pile of 12 cardboards is 35 mm, find the thickness of a pile of 294 cardboards.

Answer 1

Let x cm be the thickness of a pile of 294 cardboards.

Thickness (in cm)	3.5	x
Cardboard	12	294

$$\begin{gathered} \mathrm{Since}\mathrm{the}\mathrm{pile}\mathrm{of}\mathrm{the}\mathrm{cardboards}\mathrm{and}\mathrm{its}\mathrm{thickness}\mathrm{are}\mathrm{in}\mathrm{direct}\mathrm{variation},\mathrm{we}\mathrm{have}: \\ \frac{3.5}{x}=\frac{12}{294} \\ \Rightarrow 3.5\times 294=x\times 12 \\ \Rightarrow x=\frac{3.5\times 294}{12} \\ =\frac{1029}{12} \\ =85.75\mathrm{cm} \\ \mathrm{Thus},\mathrm{the}\mathrm{thickness}\mathrm{of}\mathrm{a}\mathrm{pile}\mathrm{of}294\mathrm{cardboards}\mathrm{will}\mathrm{be}85.75\mathrm{cm}(\mathrm{or}857.5\mathrm{mm}). \end{gathered}$$